As requirements for a data transmission rate, communication quality, and the like of mobile communications become increasingly high, an existing sub-6 GHz frequency band used in mobile communications has become very crowded. A sub-6 GHz frequency spectrum may be referred to as a low frequency (LF). A frequency spectrum above 6 GHz may be referred to as a high frequency (HF). However, in a high frequency band of 6 GHz to 300 GHz, a large quantity of frequency spectrum resources are still not allocated for use. How to effectively use a high frequency is one of research focuses in the current communications industry.
Compared with radio propagation in a sub-6 GHz frequency band, radio propagation in a high frequency band has features such as a relatively high path loss, a relatively weak capability to penetrate an obstacle, and severe rain fade or oxygen fade at some frequencies. However, a high frequency band also has features of a short wavelength and easy implementation of a large-scale array antenna. Therefore, a high path loss caused by a high frequency band may be compensated for by using a directional antenna gain brought by a beamforming technology.
However, in a high-frequency system, due to a limitation of a beam width of a directional beam, a signal sent by using one directional beam can cover only a small area in a particular direction, and corresponding information cannot be successfully received outside the area. Therefore, if an omnidirectional coverage effect in an existing mobile communications system is desired, all combinations of directional beams on a transmit end and/or a receive end need to be traversed. However, transmission is interrupted each time beam switching occurs. For a frame structure, a portion of time-frequency resources are reserved as beam switching overheads.
In a high-frequency system, in different procedures such as a synchronization procedure, a random access procedure, a signaling control procedure, a data transmission procedure, and a beam training procedure, all or some of beam combinations need to be traversed, and a guard interval required for these beam switching operations leads to high overheads of the system.